The best definition, I have found is from Web M.D Here is a short paragraph.
Tinnitus (pronounced ti-ni-tis), or ringing in the ears, is the sensation of hearing ringing, buzzing, hissing, chirping, whistling, or other sounds. The noise can be intermittent or continuous, and can vary in loudness. It is often worse when background noise is low, so you may be most aware of it at night when you’re trying to fall asleep in a quiet room. In rare cases, the sound beats in sync with your heart (pulsatile tinnitus). http://www.webmd.com/a-to-z-guides/understanding-tinnitus-basics
I have had this condition for 19 years, some days it is okay and others it is nerve racking. I tried different method’s, Brown Noises, White Noise and even Pink Noises. So I went on a web search, for on-line noise generators, I found two which I think works well enough to get me through the day. One is from AudioNotch http://www.audionotch.com/app/tune/ the other is from the American Tinnitus Association http://www.ata.org/sound . I use both, Audio Notch give you a wide range of frequency’s to match what you are hearing. The program from the American Tinnitus Association has a mixture of sounds.. I hope this helps